title: Identification and characterization of plasma membrane aquaporins isolated from fiber cells of Calotropis procera.
abstract: Calotropis procera, commonly known as "milkweed", possesses long seed trichomes for seed dispersal and has the ability to survive under harsh conditions such as drought and salinity. Aquaporins are water channel proteins expressed in all land plants, divided into five subfamilies plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), NOD26-like proteins (NIPs), small basic intrinsic proteins (SIPs), and the unfamiliar X intrinsic proteins (XIPs). PIPs constitute the largest group of water channel proteins that are involved in different developmental and regulatory mechanisms including water permeability, cell elongation, and stomata opening. Aquaporins are also involved in abiotic stress tolerance and cell expansion mechanisms, but their role in seed trichomes (fiber cells) has never been investigated. A large number of clones isolated from C. procera fiber cDNA library showed sequence homology to PIPs. Both expressed sequence tags (ESTs) and real-time polymerase chain reaction (PCR) studies revealed that the transcript abundance of this gene family in fiber cells of C. procera is greater than that of cotton. Full-length cDNAs of CpPIP1 and CpPIP2 were isolated from C. procera fiber cDNA library and used for constructing plant expression vectors under constitutive (2×35S) and trichome-specific (GhLTP3) promoters. Transgenic tobacco plants were developed via Agrobacterium-mediated transformation. The phenotypic characteristics of the plants were observed after confirming the integration of transgene in plants. It was observed that CpPIP2 expression cassette under 2×35S and GhLTP3 promoter enhanced the numbers of stem and leave trichomes. However, 2×35S::CpPIP2 has a more amplified effect on trichome density and length than GhLTP3::CpPIP2 and other PIP constructs. These findings imply the role of C. procera PIP aquaporins in fiber cell elongation. The PIPs-derived cell expansion mechanism may be exploited through transgenic approaches for improvement of fiber staple length in cotton and boosting of defense against sucking insects by enhancing plant pubescence.
authors.affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Jhang Road, Faisalabad 38000, Pakistan. wellusman@hotmail.com
authors.forename: Usman
authors.initials: U
authors.lastname: Aslam
authors.forename: Asia
authors.initials: A
authors.lastname: Khatoon
authors.forename: Hafiza Masooma Naseer
authors.initials: HM
authors.lastname: Cheema
authors.forename: Aftab
authors.initials: A
authors.lastname: Bashir
mesh_terms: D060054:Agrobacterium / Q000235:genetics; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D031107:Calotropis / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D020224:Expressed Sequence Tags; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D010539:Permeability; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics; D018547:Plant Stems / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D064201:Trichomes / Q000502:physiology; D014867:Water / Q000737:chemistry
chemical_list: D020346:Aquaporins; D018076:DNA, Complementary; D010940:Plant Proteins; D014867:Water